Split type light receiving element and circuit-built-in light-receiving element and optical disk drive

ABSTRACT

A plurality of N-type diffusion layers ( 105, 108 ) are formed a specified distance apart on a P-type semiconductor layer ( 102 ). A P-type leak prevention layer ( 109 ) formed between at least N-type diffusion layers ( 105, 108 ) prevents leaking between the diffusion layers ( 105, 108 ). A dielectric film ( 115 ) is formed in at least a light incident area on a P-type semiconductor layer ( 102 ) including the diffusion layers ( 105, 108 ) and the leak prevention layer ( 109 ). Accordingly, provided are a split type light receiving element positively functioning as a split type light receiving element even when charge is accumulated in the dielectric film and having a uniform sensitivity throughout the entire area on a light receiving surface, and a circuit-built-in light receiving element and an optical disk device using the split type light receiving element.

TECHNICAL FIELD

[0001] The present invention relates to segmented type light-receivingdevices, circuit-integrated type light-receiving devices and opticaldisk apparatuses and relates, in particular, to a segmented typelight-receiving device for use in a signal processing section of anoptical disk apparatus for a high-density DVD (Digital Versatile Disc)employing a light source of a short wavelength or the like as well as acircuit-integrated type light-receiving device and an optical diskapparatus.

BACKGROUND ART

[0002] Conventionally, an optical pickup section used in an optical diskapparatus has an optical construction in which semiconductor laser lightis concentrated on and applied to a disk by a lens, reflected light hasits light intensity modulated according to the signal written on thedisk and this reflected light is further made incident on alight-receiving device (or a circuit-integrated type light-receivingdevice in which the light-receiving device and a transistor forprocessing an electric signal taken out of this light-receiving deviceare integrated on an identical substrate). This light-receiving device(or the circuit-integrated type light-receiving device) employed in thisoptical pickup section also detects a focus signal and a servo signalaccording to the shapes of a plurality of light rays applied to andreflected on the disk besides the detection of the data signal writtenon the disk. Then, control is executed so that light is accuratelyapplied to the disk, in which the data signal is written, on the basisof the detected focus signal and servo signal.

[0003] Then, the optical pickup section employs a segmented typelight-receiving device constructed of a plurality of pn junctions thatcan receive a plurality of light rays (refer to Japanese Laid-openPublication No. H9-213920). A dielectric film is formed on thelight-receiving device surface, on which light is incident, of thesegmented type light-receiving device in order to control thereflectance on the device surface. When a single-layer oxide film isemployed as this dielectric film construction, a condition of λ/4n (nrepresents the refractive index of the oxide film, and λ represents thewavelength of light) of an optimum film thickness is satisfied, and theoxide film thickness is 70 nm with respect to, for example, light of awavelength of 400 nm. Moreover, a multilayer structure, which has a lowreflectance with respect to the wavelength to be used, is also employedas the aforementioned dielectric film construction.

[0004] As shown in FIG. 20, in the case where, for example, twolight-receiving sections are formed by providing n-type semiconductorlayers 901 and 902 on a p-type semiconductor layer 900 (there is shownnone of the electrode leads, the interlayer films and so on of then-type semiconductor layer and the p-type semiconductor layer), electriccharges are accumulated in a dielectric film 903. Therefore, an N-typeinversion layer 904 is formed by the inversion of the conductive type inthe surface of the p-type semiconductor layer 900, and the twolight-receiving sections are disadvantageously connected together bythis n-type inversion layer 904. Consequently, there is a problem thatsignals cannot be individually taken out of the two light-receivingsections and the device does not function as a segmented typelight-receiving device. The problem of the segmented typelight-receiving device easily occurs particularly when the concentrationof the p-type semiconductor layer on which the n-type semiconductorlayer is provided is reduced to improve the frequency characteristicdetermined by a CR time constant by reducing the capacitance of the pnjunction of the segmented type light-receiving device.

DISCLOSURE OF THE INVENTION

[0005] Accordingly, the object of the present invention is to provide asegmented type light-receiving device that reliably functions as asegmented type light-receiving device even if electric charges areaccumulated in the dielectric film and provide a circuit-integrated typelight-receiving device and an optical disk apparatus that employ thesegmented type light-receiving device.

[0006] In order to achieve the above object, there is provided asegmented type light-receiving device comprising:

[0007] a plurality of second conductive type diffusion layers formedspaced apart at prescribed intervals on a first conductive typesemiconductor layer;

[0008] a leakage prevention layer that is formed at least between theplurality of second conductive type diffusion layers on the firstconductive type semiconductor layer and prevents leakage between theplurality of second conductive type diffusion layers; and

[0009] a dielectric film that is formed at least in a region on whichlight is incident on the first conductive type semiconductor layerincluding the plurality of second conductive type diffusion layers andthe leakage prevention layer.

[0010] According to the segmented type light-receiving device of theabove-mentioned construction, leakage can be prevented from occurring sothat the surface of the first conductive type semiconductor layer is notinverted to the n-type of the second conductive type and the pluralityof second conductive type diffusion layers are not connected together byvirtue of the formation of the leakage prevention layer formed betweenat least the plurality of second conductive type diffusion layers on thefirst conductive type semiconductor layer in the region other than theregion in which the plurality of second conductive type diffusion layersare formed even on condition that the surface of the first conductivetype semiconductor layer is inverted to the second conductive type bythe influence of electric charges due to the dielectric film that servesas the antireflection film. Therefore, the device reliably functions asa segmented type light-receiving device even if electric charges areaccumulated in the dielectric film.

[0011] In one embodiment of the present invention, the first conductivetype semiconductor layer is exposed between the plurality of secondconductive type diffusion layers and the first conductive type leakageprevention layer.

[0012] According to the segmented type light-receiving device of theabove-mentioned embodiment, the first conductive type semiconductorlayer is exposed between the plurality of second conductive typediffusion layers and the first conductive type leakage prevention layer.Therefore, the leakage between the plurality of second conductive typediffusion layers can be reduced, and the withstand voltage across theleakage prevention layer and the second conductive type diffusion layerscan be improved.

[0013] In one embodiment of the present invention, assuming that thedielectric film has a film thickness d1 [nm] and the leakage preventionlayer has a surface concentration C1 [cm⁻³], then the film thickness d1of the dielectric film and the surface concentration C1 of the leakageprevention layer are set so as to satisfy the condition of:

d1×{square root}{square root over (C1)}≧1×1 O ¹⁰.

[0014] According to the segmented type light-receiving device of theabove-mentioned embodiment, even when the film thickness of thedielectric film is optimized for the optimization of the reflectance ofthe dielectric film, a satisfactory leakage prevention layer can beformed by satisfying the above-mentioned condition.

[0015] In one embodiment of the present invention, assuming that theleakage prevention layer has a width W1 [cm] and the leakage preventionlayer has a surface concentration C1 [cm⁻³], then the width W1 and thesurface concentration C1 of the leakage prevention layer are set so asto satisfy the condition of:

C1≦2.0×10¹⁹

[0016] when W1>4×10⁻⁵ cm and satisfy the condition of:

C1≦1.0×10²⁰×Exp(−4×10⁴ ×W1)

[0017] when W1≧4×10⁻⁵ cm.

[0018] According to the segmented type light-receiving device of theabove-mentioned embodiment, there can be obtained a segmented typelight-receiving device that has a uniform sensitivity characteristic inthe whole region of the light-receiving surface including the portion onthe leakage prevention layer.

[0019] Also, there is provided a segmented type light-receiving devicecomprising:

[0020] a plurality of second conductive type first diffusion layersformed spaced apart at prescribed intervals on a first conductive typesemiconductor layer;

[0021] a first conductive type second diffusion layer formed at leastbetween the plurality of second conductive type first diffusion layerson the first conductive type semiconductor layer; and

[0022] a dielectric film that is formed at least in a region on whichlight is incident on the first conductive type semiconductor layerincluding the plurality of second conductive type first diffusion layersand the first conductive type second diffusion layer,

[0023] the plurality of second conductive type first diffusion layersand the first conductive type second diffusion layer having a layerthickness equal to or greater than an absorption length ofshort-wavelength light.

[0024] According to the segmented type light-receiving device of theabove-mentioned construction, leakage can be prevented from occurring sothat the surface of the first conductive type semiconductor layer is notinverted to the second conductive type and the plurality of secondconductive type first diffusion layers are not connected together byvirtue of the formation of the first conductive type second diffusionlayer formed between at least the plurality of second conductive typefirst diffusion layers on the first conductive type semiconductor layerin the region other than the region in which the plurality of secondconductive type first diffusion layers are formed even on condition thatthe surface of the first conductive type semiconductor layer is invertedto the second conductive type by the influence of electric charges dueto the dielectric film that serves as the antireflection film.Furthermore, the plurality of second conductive type first diffusionlayers and the first conductive type second diffusion layer have a layerthickness equal to or greater than the absorption length of light of ashort wavelength (for example, wavelength is 350 to 450 nm). Therefore,the device has an excellent characteristic to the short-wavelength lightand reliably functions as a segmented type light-receiving device evenif electric charges are accumulated in the dielectric film.

[0025] In one embodiment of the present invention, the first conductivetype semiconductor layer is exposed between the plurality of secondconductive type first diffusion layers and the first conductive typesecond diffusion layer.

[0026] According to the segmented type light-receiving device of theabove-mentioned embodiment, the first conductive type semiconductorlayer is exposed between the plurality of second conductive type firstdiffusion layers and the first conductive type second diffusion layer.Therefore, the leakage between the plurality of second conductive typefirst diffusion layers can be reduced, and the withstand voltage acrossthe second conductive type first diffusion layer and the firstconductive type second diffusion layer can be improved.

[0027] In one embodiment of the present invention, assuming that thedielectric film has a film thickness d2 [nm] and the first conductivetype second diffusion layer has a surface concentration C2 [cm⁻³], thenthe film thickness d2 of the dielectric film and the surfaceconcentration C2 of the first conductive type second diffusion layer areset so as to satisfy the condition of:

d2×{square root}{square root over (C2)}≧1×1 O ¹⁰.

[0028] According to the segmented type light-receiving device of theabove-mentioned embodiment, even when the film thickness of thedielectric film is optimized for the optimization of the reflectance ofthe dielectric film, there can be formed the first conductive typesecond diffusion layer that has a satisfactory leakage preventionfunction by satisfying the aforementioned condition.

[0029] In one embodiment of the present invention, assuming that thefirst conductive type second diffusion layer has a width W2 [cm] and thefirst conductive type second diffusion layer has a surface concentrationC2 [cm⁻³], then the width W2 and the surface concentration C2 of thesecond diffusion layer are set so as to satisfy the condition of:

C2≦2.0×10¹⁹

[0030] when W2<4×10⁻⁵ cm and satisfy the condition of:

C2≦1.0×10²⁰×Exp(−4×10⁴ ×W2)

[0031] when W2≧4×10⁻⁵ cm.

[0032] According to the segmented type light-receiving device of theabove-mentioned embodiment, there can be obtained a segmented typelight-receiving device that has a uniform sensitivity characteristicwith respect to the short-wavelength light in the whole region of thelight-receiving surface including the first conductive type seconddiffusion layer region.

[0033] In one embodiment of the present invention, the dielectric filmis comprised of a structure in which one or a plurality of oxide filmsand one or a plurality of nitride films are alternately laminated, thefilms totally constituting at least three layers.

[0034] According to the segmented type light-receiving device of theabove-mentioned embodiment, reflectance can be reduced, and the surfaceconcentration of the leakage prevention layer can be reduced. Therefore,sensitivity can be kept satisfactory.

[0035] Also, there is provided a circuit-integrated type light-receivingdevice, wherein the above-mentioned segmented type light-receivingdevice and a signal processing circuit for processing a signal outputtedfrom the segmented type light-receiving device are formed on anidentical semiconductor substrate.

[0036] According to the circuit-integrated type light-receiving deviceof the above-mentioned construction, there can be obtained acircuit-integrated type light-receiving device of a satisfactorysensitivity characteristic.

[0037] Also, there is provided an optical disk apparatus employing theabove-mentioned segmented type light-receiving device.

[0038] Also, there is provided an optical disk apparatus employing theabove-mentioned circuit-integrated type light-receiving device.

[0039] According to the optical disk apparatus of the above-mentionedconstruction, there can be provided an optical disk apparatus thatemploys the segmented type light-receiving device or thecircuit-integrated type light-receiving device having a satisfactorysensitivity characteristic in the optical pickup section.

BRIEF DESCRIPTION OF THE DRAWINGS

[0040]FIG. 1 is a plan view showing the planar structure of a segmentedtype light-receiving device of a first embodiment of this invention;

[0041]FIG. 2 is a sectional view taken along the line 2-2 of FIG. 1;

[0042]FIG. 3A is a graph showing the relation between the lightintensity and the penetration depth of the above segmented typelight-receiving device; FIG. 3B is a cross-sectional structural view ofthe above segmented type light-receiving device;

[0043]FIG. 4 is a plan view showing the planar structure of a segmentedtype light-receiving device of a second embodiment of this invention;

[0044]FIG. 5 is a sectional view taken along the line 5-5 of FIG. 1;

[0045]FIG. 6 is a graph showing the impurity concentration distributionof a segmented type light-receiving device;

[0046]FIG. 7 is a graph showing the calculation results of reflectancewith respect to the construction of the dielectric film that serves asthe antireflection film of a segmented type light-receiving device of athird embodiment of this invention;

[0047]FIG. 8 is a graph showing the change in the surface concentrationof boron in the leakage prevention layer with respect to the dielectricfilm thickness of the above segmented type light-receiving device;

[0048]FIG. 9 is a cross-sectional structural view of a segmented typelight-receiving device whose leakage prevention layer has a small widthin a fourth embodiment of this invention;

[0049]FIG. 10 is a cross-sectional structural view of a segmented typelight-receiving device whose leakage prevention layer has a great width;

[0050]FIG. 11 is a graph showing the crosstalk characteristics of thestructures of the segmented type light-receiving devices of FIGS. 9 and10;

[0051]FIG. 12 is a graph showing the sensitivity characteristic withrespect to the width and the surface concentration of boron in theleakage prevention layer of the above segmented type light-receivingdevice;

[0052]FIG. 13 is a view showing the movement of carriers of the abovesegmented type light-receiving device;

[0053]FIG. 14 is a sectional view of a segmented type light-receivingdevice of a structure in which a p-type semiconductor layer is providedunder a p-type semiconductor film for leakage prevention;

[0054]FIG. 15 is a sectional view of a circuit-integrated typelight-receiving device of a fifth embodiment of this invention;

[0055]FIG. 16 is a schematic view showing the construction of theoptical pickup section of an optical disk apparatus that employs thesegmented type light-receiving device of a sixth embodiment of thisinvention;

[0056]FIG. 17 is a plan view showing the planar structure of a segmentedtype light-receiving device of a seventh embodiment of this invention;

[0057]FIG. 18 is a sectional view taken along the line 18-18 of FIG. 17;

[0058]FIG. 19 is a graph showing the calculation result of reflectancewith respect to a silicon oxide film of a third layer of a four-layerantireflection film; and

[0059]FIG. 20 is a sectional view showing the structure of aconventional segmented type light-receiving device.

BEST MODE FOR CARRYING OUT THE INVENTION

[0060] The segmented type light-receiving device, circuit-integratedtype light-receiving device and optical disk apparatus of this inventionwill be described in detail below on the basis of the embodimentsthereof shown in the drawings.

[0061] (First Embodiment)

[0062]FIG. 1 is a plan view showing the planar structure of thesegmented type light-receiving device of the first embodiment of thisinvention, and FIG. 2 is a sectional view taken along the line 2-2 ofFIG. 1. In the segmented type light-receiving device of this firstembodiment, the structure (for example, multilayer interconnections,interlayer films and so on) formed subsequent to the metalinterconnection processing step is not shown. Moreover, the dielectricfilm 115 shown in FIG. 2 is not shown in FIG. 1 for the sake of easinessin viewing the figure.

[0063] As shown in FIGS. 1 and 2, a first p-type semiconductor layer 101that has a thickness of 1 μm and a boron concentration of 1×10¹⁸ cm⁻³ isformed on a p-type semiconductor substrate 100 (for example, siliconsubstrate) that has a boron concentration of 1×10¹⁵ cm⁻³. A secondp-type semiconductor layer 102 as a first conductive type semiconductorlayer that has, for example, a thickness of 14 to 16 μm and a boronconcentration of about 1×10¹⁴ to 1×10¹⁵ cm⁻³ is formed on the firstp-type semiconductor layer 101. A third p-type semiconductor layer 103for anode contact formation is formed downwardly from the surface of thethus formed second p-type semiconductor layer 102. A LOCOS region 104for element isolation is formed on the surface of the second p-typesemiconductor layer 102.

[0064] Further, n-type diffusion layers 105, 106, 107 and 108 as secondconductive type diffusion layers that have, for example, an arsenicconcentration of about 1×10¹⁹ to 1×10²⁰ cm⁻³ and a junction depth ofabout 0.1 to 0.8 μm are formed spaced apart at prescribed intervals onthe surface of the second p-type semiconductor layer 102. Cathodeelectrodes 110, 111, 112 and 113 for current. takeout are provided onthe n-type diffusion layers 105, 106, 107 and 108, respectively.

[0065] Further, a p-type leakage prevention layer 109 that has a boronconcentration of about 1×10¹⁹ cm⁻³ is formed around the n-type diffusionlayers 105, 106, 107 and 108. This p-type leakage prevention layer 109is connected to the third p-type semiconductor layer 103 for anodecontact formation, and an anode electrode 114 is formed for currenttakeout on the device surface. Then, a dielectric film 115 (for example,oxide film) for preventing light from being reflected on the surface isformed to a film thickness of 70 nm in the region to which light isapplied on the second p-type semiconductor layer 102.

[0066] The structure of the aforementioned segmented typelight-receiving device will be described more in detail below.

[0067] Depletion layers 116 are formed in the p-type semiconductor layer102 by pn junctions formed of the n-type diffusion layers 105 through108 provided on the second p-type semiconductor layer 102. Electronsgenerated in the depletion layers 116 by light applied to this regionflow through the n-type diffusion layers 105 through 108 and are takenout of the cathode electrodes (110, 111, 112 and 113 shown in FIG. 1).Conversely, holes generated in the depletion layers 116 flow through thesecond p-type semiconductor layer 102 and are taken out of the anodeelectrode 114. For example, when light is applied onto the n-typediffusion layer 105, a photocurrent is taken out of the cathodeelectrode 110 and the anode electrode 114. Likewise, when light isapplied to the other n-type diffusion layers 106, 107 and 108, aphotocurrent is taken out of the cathode electrodes 111, 112 and 113corresponding to the n-type diffusion layers 106, 107 and 108,respectively, and the anode electrode 114. The quantity of light appliedto the segmented type light-receiving device can be thus estimated.

[0068] It is preferred that light is wholly absorbed in the depletionlayers 116 formed of the pn junctions formed by the n-type diffusionlayers 105 through 108. FIG. 3A shows the degree of absorption of lightthat has a wavelength of about 400 nm incident on the silicon withrespect to a penetration depth, and FIG. 3B shows a sectional view ofthe device. In FIG. 3A, the horizontal axis represents the lightintensity, while the vertical axis represents the penetration depth(μm). As is apparent from FIGS. 3A and 3B, the absorption length becomesabout 0.2 μm at a wavelength of 400 nm (absorption coefficient is about50000 cm⁻¹). That is, assuming that the light intensity is I, theintensity of incident light is I₀, the absorption coefficient is a andthe penetration depth is d, then the light intensity I is expressed as:

I=I ₀×exp^(−αd)

[0069] and, since the absorption length of light is the penetrationdepth when the intensity I₀ of the incident light becomes 1/e (≈3.67),the penetration depth d, i.e., the absorption length satisfies theequation:

−αd=−1

[0070] wherein the absorption coefficient a is about 50000 cm⁻¹,absorption length of about 0.2 μm is obtained. Therefore, the filmthickness of the n-type diffusion layers 105 through 108 shouldpreferably be set to about 0.2 to 1 μm.

[0071] Moreover, as shown in FIGS. 1 and 2, the p-type leakageprevention layer 109 doped more highly than the second p-typesemiconductor layer 102 is formed in the regions other than the n-typesemiconductor layer 102. Consequently, in the regions other than theregions in which the n-type diffusion layers 105 through 108 are formed,no inversion to the n-type occurs by virtue of the formation of thep-type leakage prevention layer 109 of a high surface concentration evenon condition that the surface of the second p-type semiconductor layer102 is inverted to the n-type by the influence of electric charges dueto the dielectric film 115 that serves as the antireflection film,making it possible to restrain the problem that the n-type diffusionlayers are connected together to fail in functioning as a segmented typelight-receiving device.

[0072] Moreover, the depletion layers 116 formed in the second p-typesemiconductor layer 102 by the n-type diffusion layers 105 through 108and the second p-type semiconductor layer 102 are scarcely influenced bythis p-type leakage prevention layer 109, and there occurs only anincrease in the capacitance component due to the comparatively highlydoped n-type semiconductor layer and the p-type leakage preventionlayer. Consequently, a junction capacitance formed in this region can bemade roughly equivalent to the case where this p-type leakage preventionlayer 109 is not provided even when the concentration of the secondp-type semiconductor layer 102 is reduced, and the frequencycharacteristic of the device determined by a CR time constant can bekept satisfactory.

[0073] Furthermore, since the p-type leakage prevention layer 109 isformed of the p-type diffusion layer, there can also be obtained theeffect that, even when light is applied to the region of this leakageprevention layer 109, this portion has a satisfactory sensitivitycharacteristic.

[0074] The function of the leakage prevention layer of the segmentedtype light-receiving device of this invention can be applied to thedevice in which the p-type and n-type conductive types of this firstembodiment are exchanged.

[0075] Moreover, although arsenic is employed as the impurity of then-type diffusion layer, it is acceptable to employ another impurity suchas phosphorus. Although boron is employed as the impurity of the p-typediffusion layer, it is acceptable to employ another impurity such asindium.

[0076] Moreover, the concentration, layer thickness and so on of thesecond p-type semiconductor layer 102 are not limited to those describedin connection with this first embodiment.

[0077] Moreover, the arrangement, configurations and so on of the anodeelectrode and the cathode electrode are not limited to those describedin connection with this first embodiment. Moreover, although this firstembodiment is based on the case of the quadrisected segmented typelight-receiving device, the leakage prevention layer described in thisinvention can be applied also to a bisected or another segmented typelight-receiving device of another segmented configuration.

[0078] (Second Embodiment)

[0079]FIG. 4 is a plan view showing the planar structure of thesegmented type light-receiving device of the second embodiment of thisinvention, and FIG. 5 is a sectional view taken along the line 5-5 inFIG. 4. In the segmented type light-receiving device of this secondembodiment, the structure (for example, multilayer interconnections,interlayer films and so on) formed subsequent to the metalinterconnection processing step is not shown.

[0080] As shown in FIGS. 4 and 5, a first p-type semiconductor layer 201that has a thickness of 1 μm and a boron concentration of 1×10¹⁸ cm⁻³ isformed on a p-type semiconductor substrate 200 (for example, siliconsubstrate) that has a boron concentration of 1×10¹⁵ cm⁻³. A secondp-type semiconductor layer 202 that has, for example, a thickness of 14to 16 μm and a boron concentration of about 1×10¹⁴ to 1×10¹⁵ cm⁻³ isformed on the first p-type semiconductor layer 201. A third p-typesemiconductor layer 203 for anode contact formation is formed downwardlyfrom the surface of the thus formed second p-type semiconductor layer202. A LOCOS region 204 for element isolation is formed on the surfaceof the second p-type semiconductor layer 202.

[0081] N-type diffusion layers 205 and 206 as second conductive typefirst diffusion layers that have, for example, an arsenic concentrationof about 1×10¹⁹ to 1×10²⁰ cm⁻³ and a junction depth of about 0.1 to 0.8μm are formed spaced apart at prescribed intervals on the surface of thesecond p-type semiconductor layer 202. Cathode electrodes 208 and 209for current take out are provided on the n-type diffusion layers 205 and206, respectively. Then, a p-type leakage prevention layer 207 as afirst conductive type second diffusion layer that has, for example, aboron concentration of 5×10¹⁸ cm⁻³ and a junction depth of about 0.3 μmfor preventing leakage is formed in a region located between the n-typediffusion layers 205 and 206.

[0082] Further, a dielectric film (oxide film) 211 and a dielectric film(nitride film) 212, which serve as an antireflection film, are formed atleast in the region to which light is applied on the second p-typesemiconductor layer 202. Further, an anode electrode 210 is formed onthe third p-type semiconductor layer 203. The numeral 213 denotes adepletion layer.

[0083] Even with the above-mentioned structure, the n-type diffusionlayers 205 and 206 are not connected together by virtue of the p-typeleakage prevention layer 207 in the portion on the surface of which thesecond p-type semiconductor layer 202 is exposed even when inversion iscaused by electric charges due to the dielectric films (211 and 212),and the device reliably functions as a segmented type light-receivingdevice.

[0084]FIG. 6 shows the arsenic and boron concentration profiles in aposition of about 0.2 μm apart from the surface along the cross sectionof the dashed line A shown in FIG. 4 in the structure of the segmentedtype light-receiving device of the second embodiment. Since the secondp-type semiconductor layer 202 is exposed between the n-type diffusionlayer 205 and the p-type leakage prevention layer 207, leakageprevention and a withstand voltage across the n-type diffusion layer andthe p-type leakage prevention layer can be improved by adopting thestructure of this second embodiment in comparison with the case wherethe comparatively highly doped n-type semiconductor layer and the p-typediffusion layer that serves as the leakage prevention layer are put incontact with each other as described in connection with the firstembodiment. Furthermore, since the comparatively highly doped layers ofthe opposite conductive types are not put in contact with each other,the junction capacitance in this portion is allowed to be reduced andmade equivalent to the total capacitance of the whole device in which nop-type leakage prevention layer is provided, and the responsecharacteristic of the device determined by the CR time constant can alsobe kept satisfactory.

[0085] In this second embodiment, the concentration, layer thickness andso on of each semiconductor layer are not limited to those described inconnection with the second embodiment, and the p-type diffusion layerthat serves as the p-type leakage prevention layer may be formed of BF²or the like.

[0086] Moreover, the constructions of the dielectric films (211 and 212)formed on the second p-type semiconductor layer 202 are not limited tothose described in connection with the second embodiment but allowed toadopt various materials and constructions.

[0087] Moreover, the electrode structure, the shape and number of thelight-receiving surface and so on are not limited to those described inconnection with this second embodiment.

[0088] (Third Embodiment)

[0089] The segmented type light-receiving device of the third embodimentof this invention will be described next. The layer structure of thesegmented type light-receiving device of this third embodiment has thesame construction as that of the segmented type light-receiving deviceof the second embodiment, and FIGS. 4 and 5 should be correspondinglyreferred to for the structure.

[0090] In the segmented type light-receiving device of this thirdembodiment, the film thickness of the dielectric films 211 and 212provided on the second p-type semiconductor layer 202 is set so thatincident light is efficiently made incident on the light-receivingdevice.

[0091]FIG. 7 shows the calculation results of surface reflectance whenthe film thickness of the dielectric film (oxide film) 211 is changedrelative to the film thickness of the dielectric film (nitride film) 212with respect to light of a wavelength of 400 nm. As is apparent fromFIG. 7, it can be understood that the film thickness of the dielectricfilm (nitride film) 212 and the film thickness of the dielectric film(oxide film) 211 are required to be optimized in order to reduce thereflectance, and it is preferable to reduce the film thickness of thedielectric film (oxide film) 211 and increase the film thickness of thedielectric film (nitride film) 212 with respect to light of a wavelengthof about 400 nm.

[0092]FIG. 8 shows the results of measuring a leakage current betweendifferent cathodes when the surface concentration of boron in the p-typeleakage prevention layer 207 is changed by changing this oxide filmthickness in the device structure of the segmented type light-receivingdevice of this second embodiment. According to this result, it can beunderstood that the leakage current between the cathodes cannot berestrained as the film thickness of the dielectric film (oxide film) 211is reduced in the case of the p-type leakage prevention layer 207 thathas same surface concentration. The reason for the above is thatelectric charges are accumulated at the interface between the oxide filmand the nitride film in the antireflection film, and when the electriccharges are positive charges, electrons are accumulated on the surfaceof the p-type leakage prevention layer 207 to form an n-type inversionlayer region, disadvantageously causing an electrical connection betweenthe n-type diffusion layers 205 and 206 that serve as a plurality ofcathodes.

[0093] In order to prevent this, the p-type leakage prevention layer 207that has a prescribed surface concentration is provided. However, it hasbeen discovered that an electric field intensity due to electric chargesis increased when the film thickness of the dielectric film (oxide film)211 is small even when the amount of charges accumulated at thedielectric interface is constant and the concentration of the p-typeleakage prevention layer 207 is constant and the inversion of the secondp-type semiconductor layer more easily occurs. Consequently, the n-typediffusion layers 205 and 206 are disadvantageously electricallyconnected together, and therefore, the surface concentration of thep-type leakage prevention layer 207 is required to be increased in orderto prevent this.

[0094] As a result of examining this relation more in detail, it hasbeen discovered that it is proper to set the relation between a surfaceconcentration C1 [cm⁻³] of the p-type diffusion layer that serves as theleakage prevention layer and the dielectric film thickness (oxide filmthickness) d1 [nm] that serves as the antireflection film as:

d1×{square root}{square root over (C2)}≧1×1 O ¹⁰.

[0095] For example, it is preferable to set the nitride film to 40 nmand set the oxide film to 10 nm in order to restrain the surfacereflectance to 2.5%. In this case, the concentration of the p-typeleakage prevention layer 207 is required to be set to 1×10¹⁸ [cm⁻³] ormore.

[0096] With the above arrangement, the leakage between the n-typediffusion layers 205 and 206 that serve as the cathodes can berestrained, and the device reliably functions as a segmented typelight-receiving device.

[0097] With regard to the effects of the segmented type light-receivingdevice of this third embodiment, the inversion of the conductive typeoccurs as a consequence of the accumulation of electric charges on thesurface or in the vicinity of the surface of this oxide film even whenthe dielectric film that serves as the antireflection film is providedwith a single-layer structure of an oxide film. Therefore, by settingthe thickness of the dielectric film that satisfies the aforementionedrelation, this problem can be restrained.

[0098] With regard to the conductive type of the structure described inconnection with this third embodiment, similar effects can be obtainedeven when the n-type is changed to p-type and the p-type is changed ton-type.

[0099] (Fourth Embodiment)

[0100] The segmented type light-receiving device of the fourthembodiment of this invention will be described next. The segmented typelight-receiving device of this fourth embodiment has the sameconstruction as that of the segmented type light-receiving device of thesecond embodiment.

[0101] As shown in FIG. 9, when light is applied to the region of n-typediffusion layers 305 and 306 as second conductive type first diffusionlayer that serves as a cathode formed on a p-type semiconductor layer302 (light is applied to 306 in FIG. 9), electrons generated in thisregion are taken out of cathode electrodes (not shown) provided on then-type diffusion layers 305 and 306. In contrast to this, holes aretaken out of an anode electrode (not shown) that is a p-type leakageprevention layer 307 as a first conductive type second diffusion layerlocated on the substrate side.

[0102] However, when light is applied to the region of the p-typeleakage prevention layer 307, the generated electrons are taken out ofeach cathode electrode at an approximately equal rate. Consequently,when light is applied while being scanned, cathodic currents taken outof the cathode electrodes are varied depending on the width of thep-type leakage prevention layer 307. That is, the state in which thecathodic current is taken out changes depending on when the width of thep-type leakage prevention layer 307 is small as shown in FIG. 9 and whenthe width of the p-type leakage prevention layer 307 is great as shownin FIG. 10. FIG. 11 shows output characteristics (crosstalkcharacteristics) from the cathode electrodes when the light applicationposition is scanned in the direction of arrow (from the left-hand sidetoward the right-hand side in the figure) in FIGS. 9 and 10. In FIG. 11,there are shown an output Ach of a cathode (306) and an output Bch of acathode (305) of FIG. 9 as well as an output Cch of the cathode (306)and an output Dch of the cathode (305) of FIG. 10.

[0103] Due to the aforementioned characteristics possessed, it isrequired to optimize the width of the p-type leakage prevention layer307 according to applications. FIG. 12 shows the results of measuringthe sensitivity when the width and concentration of the p-type leakageprevention layer 307 are changed in this case. The sensitivity curveshown in this FIG. 12 shows a region that has the same sensitivity asthat of the n-type semiconductor layer of the cathode region and has auniform sensitivity characteristic in the surface of the light-receivingdevice. As is apparent from FIG. 12, the sensitivity reduces as thewidth of the p-type leakage prevention layer 307 increases.

[0104] This is because light is absorbed in the vicinity of the devicesurface in the case of light that has a great absorption coefficient inthe silicon substrate like short-wavelength light. Electrons and holes,which are generated by light applied to the cathode region at this time,flow toward the n-type diffusion layer and the substrate side. Incontrast to this, electrons of the minority carriers among the carriersgenerated in the surface of the p-type diffusion layer 307 that servesas the leakage prevention layer, diffuse in the vicinity of the surfaceof the p-type leakage prevention layer 307 and reach the n-typediffusion layers 305 and 306 that serve as the cathodes as shown in FIG.13. Therefore, when the concentration of the p-type leakage preventionlayer 307 is high, the lifetime of the electrons that serve as theminority carriers is reduced, and therefore, the electrons come tocontribute nothing to a photoelectric current. That is, this stateoccurs when the width of the region of the p-type leakage preventionlayer 307 is greater than the diffusion length of the electrons thatserve as the generated minority carriers. Consequently, the sensitivityin the p-type leakage prevention layer 307 is reduced.

[0105] Accordingly, as a result of measuring the sensitivity in thisregion by changing the width W1 [cm] and the surface concentration C1[cm⁻³] of the semiconductor layer of the p-type leakage prevention layer307, it is preferable to form the p-type leakage prevention layer 307 sothat the relation of:

C1≦2.0×10¹⁹

[0106] is maintained when W1<4×10⁻⁵ cm and the relation of:

C1≦1.0×10²⁰×Exp(−4×10⁴ ×W1)

[0107] is maintained when W1≧4×10⁻⁵ cm. With the above arrangement, thereduction in the sensitivity of the p-type leakage prevention layer 307is prevented.

[0108] In the dielectric films (311, 312) of the two-layer structure ofthe nitride film and the oxide film, it is preferable to set the filmthickness of the nitride film to 40 nm and set the film thickness of theoxide film to 10 nm in order to restrain the reflectance to, forexample, 2.5%. In this case, the concentration of the p-type leakageprevention layer 307 is required to be set to 1×10¹⁸ cm⁻³ or more. Thatis, in order to set the sensitivity in the region of this p-type leakageprevention layer 307 equal to that of the n-type diffusion layers 305and 306 that serve as the cathode sections, the width W1 of the p-typeleakage prevention layer 307 is required to be set to 11.5 μm or less.

[0109] The p-type leakage prevention layer 307 may have anyconstruction. Furthermore, since the surface concentration and the widthof the p-type leakage prevention layer contribute only to thesensitivity, there may be provided, for example, a structure in which ap-type diffusion layer is provided under the p-type leakage preventionlayer as shown in FIG. 14.

[0110] That is, as shown in FIG. 14, a first p-type semiconductor layer401 and a second p-type semiconductor layer 402 are successively formedon a p-type semiconductor substrate 400, and a third p-typesemiconductor layer 403 for anode contact formation is formed downwardlyfrom the surface of the second p-type semiconductor layer 402. A LOCOSregion 404 for element isolation is formed on the surface of the secondp-type semiconductor layer 402. Further, n-type diffusion layers 405 and406 are formed on the surface of the second p-type semiconductor layer402, and a cathode electrode (not shown) for current take out isprovided on each of the n-type diffusion layers 405 and 406. A p-typeleakage prevention layer 407 for preventing the leakage is formed in theregion located between the n-type diffusion layers 405 and 406. Further,a dielectric film (oxide film) 411 and a dielectric film (nitride film)412, which serve as an antireflection film, are formed at least in theregion to which light is applied on the second p-type semiconductorlayer 402. Further, an anode electrode 410 is formed on the third p-typesemiconductor layer 403. Moreover, a p-type semiconductor layer 413 isformed under the p-type leakage prevention layer 407. This p-typesemiconductor layer 413 is allowed to have various concentrations andstructures adopted.

[0111] (Fifth Embodiment)

[0112]FIG. 15 is a sectional view showing the structure of thecircuit-integrated type light-receiving device of the fifth embodimentof this invention. In this circuit-integrated type light-receivingdevice, a segmented type light-receiving device and, for example, abipolar transistor for processing a signal obtained from the segmentedtype light-receiving device are formed on an identical semiconductorsubstrate. In the circuit-integrated type light-receiving device of thisfifth embodiment, the structure (for example, multilayerinterconnections, interlayer films and so on) formed subsequent to themetal interconnection processing step is not shown.

[0113] As shown in FIG. 15, a first p-type semiconductor layer 601 thathas a thickness of 1 to 2 μm and a boron concentration of about 1×10¹⁸to 1×10¹⁹ cm⁻³ is formed on a p-type semiconductor substrate 600 (forexample, silicon substrate) that has a boron concentration of about1×10¹⁵ cm⁻³ in order to reduce a parasitic resistance generated at theanode of the segmented type light-receiving device, and a second p-typesemiconductor layer 602 that has a film thickness of 15 to 16 μm and aboron concentration of about 1×10¹³ to 1×10¹⁴ cm⁻³ is formed. An n-typesemiconductor layer that serves as a collector 613 of an npn transistoris formed on the second p-type semiconductor layer 602. Then, a fourthp-type semiconductor layer 611 that has a film thickness of 1 to 2 μmand a boron concentration of about 1×10¹³ to 1×10¹⁴ cm⁻³ is formed onthis second p-type semiconductor layer 602. Further, A LOCOS regions 603for element isolation is formed on the fourth p-type semiconductor layer611.

[0114] Further, a plurality of n-type diffusion layers 605 and 606 assecond conductive type first diffusion layers that have, for example, aphosphorus concentration of about 1×10¹⁹ to 1×10²⁰ cm⁻³ and a junctiondepth of 0.3 to 0.8 μm and a p-type leakage prevention layer 607 as afirst conductive type second diffusion layer that has, for example, aboron concentration of 1×10¹⁸ and a width of 2 μm is formed in theregions of the plurality of n-type diffusion layers 605 and 606 on thefourth p-type semiconductor layer 611. Even when the fourth p-typesemiconductor layer 611 that forms a pn junction is made to have a highresistivity, by virtue of the p-type leakage prevention layer 607, it ispossible to prevent the conductive type of the surface of this p-typesemiconductor layer from being inverted by the positive charges at theantireflection film interface and prevent the n-type diffusion layers605 and 606 from being electrically connected together.

[0115] Moreover, a dielectric film (oxide film) 604 and a dielectricfilm (nitride film) 610, which serve as an antireflection film, areformed at least in the region to which light is applied on the fourthp-type semiconductor layer 611. Further, in order to form metalinterconnections of the first p-type semiconductor layer 601 on thesubstrate surface, third p-type semiconductor layers 608 and 609 thathave a boron concentration of about 1×10¹⁸ to 1×10¹⁹ cm⁻³ are formed.

[0116] Further, an n-type well structure 612 that has, for example, aphosphorus concentration of 2×10¹⁵ to 2×10¹⁶ cm⁻³ is formed in thefourth p-type semiconductor layer 611 that serves as a transistorregion. An n-type diffusion layer, which has, for example, a phosphorusconcentration of 1×10¹⁹ to 2×10¹⁹ cm⁻³ and serves as a collector contact614 of the transistor, is formed in one region of the n-type wellstructure 612. Then, a p-type diffusion layer, which has, for example, aboron concentration of 1×10¹⁷ to 2×10¹⁷ cm⁻³ and serves as the base 615of the transistor is formed in one region of the n-type well structure612, and an n-type diffusion layer that serves as an emitter 616 isformed by solid phase diffusion from the polysilicon in which arsenic isimplanted. Then, a cathode electrode (not shown) and an anode electrode617 of this segmented type light-receiving device as well as a collectorelectrode 618, a base electrode 619 and an emitter electrode 620 of thetransistor are formed. A circuit-integrated type light-receiving deviceof satisfactory characteristics can be obtained with the segmented typelight-receiving device as described above.

[0117] Although the structure of the segmented sections of the segmentedtype light-receiving device in the circuit-integrated typelight-receiving device of this fifth embodiment is the one described inconnection with the second embodiment, there may be employed the onedescribed in any other embodiment. Moreover, although the npn-typetransistor is employed, there may be a structure that employs a pnp-typetransistor or both of the structures.

[0118] Moreover, the structure of the transistor and so on is notlimited to the one described in connection with this fifth embodiment,and a variety of structures can be employed.

[0119] (Sixth Embodiment)

[0120]FIG. 16 shows a schematic view showing the construction of theoptical pickup section of an optical disk apparatus that employs thesegmented type light-receiving device of the sixth embodiment of thisinvention.

[0121] As shown in FIG. 16, light emitted from a semiconductor laser 700is split into three light beams of two side beams for tracking and amain beam for signal reading by a diffraction grating 701 for generatinga tracking beam. Then, these light beams are transmitted as zeroth-orderlight beams through a hologram device 702, transformed into parallellight beams by a collimator lens 703 and thereafter concentrated on adisk surface 705 by an object lens 704. This concentrated light has itsoptical intensity modulated by pits formed on the disk surface 705 andis reflected, transmitted through the object lens 704 and the collimatorlens 703 and thereafter diffracted by the hologram device 702. Thisfirst-order light component is made incident on a segmented typelight-receiving device 706 constructed of five segmented light-receivingsections D1 through D5. Then, by adding and subtracting outputs from thefive segmented light-receiving sections D1 through D5, a signal forsignal reading and a signal for tracking can be obtained. It isacceptable to employ a circuit-integrated type light-receiving devicewith a segmented type light-receiving device in place of the segmentedtype light-receiving device.

[0122] By employing the segmented type light-receiving device of thisinvention for the optical disk apparatus that has the optical pickupsection as described above, a high-speed high-density optical diskapparatus corresponding to a short wavelength can be obtained.

[0123] It is possible to unlimitedly adopt the structure of thesegmented type light-receiving device of this invention and thecircuit-integrated type light-receiving device that employs it not onlyfor the segmented type light-receiving device that has thelight-receiving surface described in connection with the sixthembodiment but also for those which have at least a pn junction to whicha plurality of light rays are applied.

[0124] Moreover, the segmented type light-receiving device and thecircuit-integrated type light-receiving device of this invention can beunlimitedly applied not only to the optical system of the sixthembodiment but also to various optical systems and optical diskapparatuses constructed of an optical pickup section that employ thesame.

[0125] (Seventh Embodiment)

[0126]FIG. 17 is a plan view showing the planar structure of thesegmented type light-receiving device of the seventh embodiment of thisinvention, and FIG. 18 is a sectional view taken along the line 18-18 ofFIG. 17. In the segmented type light-receiving device of this seventhembodiment, the structure (for example, multilayer interconnections,interlayer films and so on) formed subsequent to the metalinterconnection processing step is not shown.

[0127] As shown in FIGS. 17 and 18, a first p-type semiconductor layer801 that has a thickness of 1 μm and a boron concentration of 1×10¹⁸cm⁻³ is formed on a p-type semiconductor substrate 800 (for example,silicon substrate) that has a boron concentration of 1×10¹⁵ cm⁻³. Asecond p-type semiconductor layer 802 that has, for example, a thicknessof 14 to 16 μm and a boron concentration of about 1×10¹⁴ to 1×10¹⁵ cm⁻³is formed on the first p-type semiconductor layer 801. A third p-typesemiconductor layer 807 for anode contact is formed downwardly from thesurface of the thus formed second p-type semiconductor layer 802. ALOCOS region 803 for element isolation is formed on the surface of thesecond p-type semiconductor layer 802.

[0128] Further, n-type diffusion layers 805 and 806 as second conductivetype first diffusion layers that have, for example, an arsenicconcentration of about 1×10¹⁹ to 1×10²⁰ cm⁻³ and a junction depth ofabout 0.1 μm to 0.8 μm are formed spaced apart at prescribed intervalson the surface of the second p-type semiconductor layer 802. Cathodeelectrodes 813 and 814 for current take out are provided on the n-typediffusion layers 805 and 806, respectively. Then, a p-type leakageprevention layer 804 as a first conductive type second diffusion layerfor preventing leakage is provided in a region located between then-type diffusion layers 805 and 806.

[0129] Further, a dielectric film (for example, silicon oxide film) 809,a dielectric film (for example, silicon nitride film) 810, a dielectricfilm (for example, silicon oxide film) 811 and a dielectric film (forexample, silicon nitride film) 812, which serve as an antireflectionfilm, are formed to have a four-layer structure at least in the regionto which light is applied on the second p-type semiconductor layer 802.Further, an anode electrode 808 is formed on the third p-typesemiconductor layer 807.

[0130] With the above-mentioned structure, no leakage occurs in theportion on the surface of which the second p-type semiconductor layer802 is exposed since the n-type diffusion layers 805 and 806 are notconnected together by virtue of the p-type leakage prevention layer 804even when inversion is caused by an electric field due to, for example,electric charges injected from the surface into the four-layerdielectric films (809 through 812). Therefore, the device reliablyfunctions as a segmented type light-receiving device.

[0131] Effects obtained by an antireflection film that has a structureof four or more layers of oxide films and nitride films will bedescribed more in detail below.

[0132]FIG. 7 shows the calculation results of the reflectance dependencyof a two-layer antireflection film constructed of a silicon oxide filmand a silicon nitride film with respect to film thickness. It can beunderstood from FIG. 7 that the reflectance of the two-layerantireflection film can be reduced as the silicon oxide film thicknessis reduced and the silicon nitride film thickness is increased. Forexample, in the case where the silicon oxide film thickness is 10 nm andthe silicon nitride film thickness is 40 nm, the reflectance can bereduced down to 2.5%.

[0133] Moreover, FIG. 8 shows the relation of leakage current withrespect to the surface concentration of the leakage prevention layer andthe silicon oxide film thickness. As is apparent from FIG. 8, it can beunderstood that the surface concentration of the leakage preventionlayer must be increased as the silicon oxide film thickness is reducedin order to prevent the inversion in the semiconductor surface.

[0134] Further, when the leakage prevention layer has a width requiredby the crosstalk characteristic of the segmented sections according toFIG. 12, there occurs a problem that the sensitivity of the leakageprevention layer cannot be obtained when the concentration of theleakage prevention layer is increased.

[0135] In contrast to this, FIG. 19 shows the calculation result ofreflectance (at a wavelength of 400 nm) with respect to the third-layersilicon oxide film of the four-layer antireflection film when, forexample, the first-layer silicon oxide film is formed to a thickness ofabout 20 nm, the second-layer silicon nitride film is formed to athickness of about 30 nm and the third-layer silicon nitride film andthe fourth-layer silicon nitride film are formed to a thickness of about50 nm successively on the second p-type semiconductor layer 802. Bysetting the thickness of the third-layer silicon nitride film to about66 nm, it is possible to increase the thickness of the first-layersilicon oxide film and reduce the reflectance to about 2.1%.

[0136] As a result, even when the segmented sections have a widthrequired by the crosstalk characteristic of the segmented sections, itis possible to reduce the reflectance and reduce the surfaceconcentration of the leakage prevention layer. Therefore, thesensitivity can be kept satisfactory.

[0137] Although the four-layer antireflection film is formed in thisseventh embodiment, a similar effect can be obtained even if theantireflection film is formed of a plurality of layers. For example, bysetting the first-layer silicon oxide film to a thickness of about 20nm, setting the second-layer silicon nitride film to a thickness ofabout 30 nm, setting the third-layer silicon oxide film to a thicknessof about 66 nm, setting the fourth-layer silicon nitride film to athickness of about 50 nm and setting the fifth-layer silicon oxide filmto a thickness of about 70 nm, the reflectance can be adjusted to about1.8%.

[0138] It is to be noted that the film thickness of the first-layersilicon oxide film is not limited to 20 nm but allowed to have variousvalues. In the above case, by properly adjusting the thickness of eachof the other films that constitute the antireflection film, thereflectance can be restrained.

[0139] (Eighth Embodiment)

[0140] The segmented type light-receiving device of the eighthembodiment of this invention will be described next. This eighthembodiment has a device structure in which the conductive types areinverted with respect to the structure of FIGS. 17 and 18 in a mannerthat the n-type is inverted to the p-type and the p-type is inverted tothe n-type. Therefore, although the anode electrode and the cathodeelectrode and the conductive types are inverted, this eighth embodimentwill be described using the same reference numerals correspondinglyreferring to FIGS. 17 and 18.

[0141] A first n-type semiconductor layer 801 that has a thickness of 1μm and a phosphorus concentration of 1×10¹⁸cm⁻³ is formed on an n-typesemiconductor substrate 800 (for example, silicon substrate) that has aphosphorus concentration of 1×10¹⁵ cm⁻³. A second n-type semiconductorlayer 802 that has, for example, a thickness of 14 to 16 μm and aphosphorus concentration of about 1×10¹⁴ to 1×10¹⁵ cm⁻³ is formed on thefirst n-type semiconductor layer 801. A third n-type semiconductor layer807 for anode contact is formed downwardly from the surface of the thusformed second n-type semiconductor layer 802. A LOCOS region 803 forelement isolation is formed on the surface of the second n-typesemiconductor layer 802.

[0142] Further, p-type diffusion layers 805 and 806 as second conductivetype first diffusion layers that have, for example, a boronconcentration of about 1×10¹⁹ to 1×10²⁰ cm⁻³ and a junction depth ofabout 0.1 μm to 0.8 μm are formed spaced apart at prescribed intervalson the surface of the second n-type semiconductor layer 802. Anodeelectrodes 813 and 814 for current take out are provided on the p-typediffusion layers 805 and 806, respectively. Then, an n-type leakageprevention layer 804 as a first conductive type second diffusion layerthat employs phosphorus for preventing leakage is formed in the regionlocated between the p-type diffusion layers 805 and 806.

[0143] Further, a dielectric film (for example, silicon oxide film) 809,a dielectric film (for example, silicon nitride film) 810, a dielectricfilm (for example, silicon oxide film) 811 and a dielectric film (forexample, silicon nitride film) 812, which serve as an antireflectionfilm, are formed to have a four-layer structure at least in the regionto which light is applied on the second n-type semiconductor layer 802.Further, a cathode electrode 808 is formed on the third n-typesemiconductor layer 807.

[0144] Even with the above-mentioned structure, the p-type diffusionlayers 805 and 806 are not connected together by virtue of the n-typeleakage prevention layer 804 in the portion on the surface of which thesecond n-type semiconductor layer 802 is exposed even when inversion iscaused by electric charges due to the dielectric films of theantireflection film, and the device reliably functions as a segmentedtype light-receiving device.

[0145] Moreover, although the four-layer antireflection film isdescribed in connection with this eighth embodiment, the presentembodiment is not limited to this but allowed to be an antireflectionfilm of a plurality of layers.

[0146] Moreover, arsenic or the like can be employed for n-type doping.

[0147] Moreover, the segmented type light-receiving device of thisinvention, which has a satisfactory characteristic with respect to lightof a short wavelength and has sensitivity to light of the wavelengths ofred, infrared and similar rays (the absorption coefficient is small, andphotocarriers are generated in a comparatively deep region of thedevice), can therefore be applied also to optical disk apparatuses formulti-wavelength read and write.

[0148] In the segmented type light-receiving device of this invention,it is acceptable to provide a resin film that has optical transparencyon the dielectric film formed at least in the region on which light isincident on the semiconductor layer.

1. A segmented type light-receiving device comprising: a plurality ofsecond conductive type diffusion layers (105-108, 205, 206) formedspaced apart at prescribed intervals on a first conductive typesemiconductor layer (102, 202); a leakage prevention layer (109, 207)that is formed at least between the plurality of second conductive typediffusion layers (105-108, 205, 206) on the first conductive typesemiconductor layer (102, 202) and prevents leakage between theplurality of second conductive type diffusion layers (105-108, 205,206); and a dielectric film (115, 211, 212) that is formed at least in aregion on which light is incident on the first conductive typesemiconductor layer (102, 202) including the plurality of secondconductive type diffusion layers (105-108, 205, 206) and the leakageprevention layer (109, 207).
 2. The segmented type light-receivingdevice as claimed in claim 1, wherein the first conductive typesemiconductor layer is exposed between the plurality of secondconductive type diffusion layers (205, 206) and the first conductivetype leakage prevention layer (207).
 3. The segmented typelight-receiving device as claimed in claim 1, wherein, assuming that thedielectric film (211) has a film thickness d1 [nm] and the leakageprevention layer (207) has a surface concentration C1 [cm⁻³], then thefilm thickness d1 of the dielectric film (211) and the surfaceconcentration C1 of the leakage prevention layer (207) are set so as tosatisfy the condition of: d1×{square root}{square root over (C1)}≧1×10¹⁰.
 4. The segmented type light-receiving device as claimed in claim 1,wherein, assuming that the leakage prevention layer (307) has a width W1[cm] and the leakage prevention layer (307) has a surface concentrationC1 [cm⁻³], then the width W1 and the surface concentration C1 of theleakage prevention layer (307) are set so as to satisfy the conditionof: C1≦2.0×10¹⁹ when W1<4×10⁻⁵ cm and satisfy the condition of:C1≦1.0×10²⁰×Exp(−4×10⁴ ×W1) when W1≧4×10⁻⁵ cm.
 5. A segmented typelight-receiving device comprising: a plurality of second conductive typefirst diffusion layers (205, 206) formed spaced apart at prescribedintervals on a first conductive type semiconductor layer (202); a firstconductive type second diffusion layer (207) formed at least between theplurality of second conductive type first diffusion layers (205, 206) onthe first conductive type semiconductor layer (202); and a dielectricfilm (211, 212) that is formed at least in a region on which light isincident on the first conductive type semiconductor layer (202)including the plurality of second conductive type first diffusion layers(205, 206) and the first conductive type second diffusion layer (207),the plurality of second conductive type first diffusion layers (205,206) and the first conductive type second diffusion layer (207) having alayer thickness equal to or greater than an absorption length ofshort-wavelength light.
 6. The segmented type light-receiving device asclaimed in claim 5, wherein the first conductive type semiconductorlayer (202) is exposed between the plurality of second conductive typefirst diffusion layers (205, 206) and the first conductive type seconddiffusion layer (207).
 7. The segmented type light-receiving device asclaimed in claim 5, wherein, assuming that the dielectric film (211) hasa film thickness d2 [nm] and the first conductive type second diffusionlayer (207) has a surface concentration C2 [cm⁻³], then the filmthickness d2 of the dielectric film (211) and the surface concentrationC2 of the first conductive type second diffusion layer (207) are set soas to satisfy the condition of: d2×{square root}{square root over(C2)}≧1×1 0¹⁰.
 8. The segmented type light-receiving device as claimedin claim 5, wherein, assuming that the first conductive type seconddiffusion layer (307) has a width W2 [cm] and the first conductive typesecond diffusion layer (307) has a surface concentration C2 [cm⁻³], thenthe width W2 and the surface concentration C2 of the second diffusionlayer (307) are set so as to satisfy the condition of: C2≦2.0×10¹⁹ whenW2<4×10⁻⁵ cm and satisfy the condition of: C2≦1.0×10²⁰×Exp(−4×10⁴ ×W2)when W2≧4×10⁻⁵ cm.
 9. The segmented type light-receiving device asclaimed in claim 1, wherein the dielectric film (809-812) is comprisedof a structure in which one or a plurality of oxide films and one or aplurality of nitride films are alternately laminated, the films totallyconstituting at least three layers.
 10. A circuit-integrated typelight-receiving device, wherein the segmented type light-receivingdevice claimed in claim 1 and a signal processing circuit for processinga signal outputted from the segmented type light-receiving device areformed on an identical semiconductor substrate (600).
 11. An opticaldisk apparatus employing the segmented type light-receiving device (706)claimed in claim 1 or the circuit-integrated type light-receiving deviceclaimed in claim 10.